1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to adaptively controlling a turn-on time of a transceiver in a Zigbee network.
2. Description of Related Art
A wireless ad hoc network environment is synchronized by a device serving as a coordinator. That is, as for the IEEE 802.11 standard, all devices connecting with a wireless ad hoc network can serve as a coordinator for synchronizing the wireless ad hoc network environment for every beacon frame by using the backoff algorithm.
Meanwhile, in specifications of the IEEE 802.15.1 standard called Bluetooth, the IEEE 802.15.3 and IEEE 803.15.3a standards for high-data-rate wireless personal area network (WPAN), and the IEEE 802.15.4 standard called Zigbee for low-data-rate WPAN, only one coordinator exists while the wireless ad hoc network environment is maintained. Accordingly, beacon frames generated by one coordinator are broadcasted to devices connected to the network at stated periods, so that all the devices are synchronized. That is, each device keeps synchronized by receiving the beacon frames from the coordinator.
FIG. 1 illustrates a Zigbee network configuration in accordance with the related art.
With reference to FIG. 1, a plurality of devices 10, 12, 14, 16 and 18 constitutes a network, and one device 10 in the network serves as a coordinator. The device 10 periodically broadcasts beacon frames, which are synchronization signals, to the other devices 12, 14, 16 and 18, and synchronizes the devices connected to the network. FIG. 1 shows one coordinator 10 and four devices 10, 14, 16 and 18 as a matter of convenience for description, but the number of the devices is not limited to four, and a larger or smaller number of devices can be connected to the ad hoc network.
For the devices to receive beacon frames transmitted from the coordinator, transceivers in the corresponding devices should be turned on. The devices turn on the transceivers considering time errors between timers incorporated in the coordinator and in themselves, and a transmission period of the beacon frames. Meanwhile, the transmission period of the beacon frame is determined by the beacon order ranging from zero (0) to fourteen (14), and the time errors between the coordinator and the devices increase as the transmission period of the beacon frames becomes longer.
FIG. 2 illustrates a timing diagram showing a turn-on time of a transceiver when each device receives beacon frames from a coordinator. Referring to FIG. 2, in a Zigbee system in accordance with the related art, it is assumed that the transmission period of the beacon frames is fixed, so that the transceiver is turned on at a predetermined fixed time. Generally, let the longest transmission period be about 126,000 milliseconds. At this time, the transceiver is turned on at a predetermined fixed time corresponding to the longest transmission period considering some time error.
However, the related art method has a problem that it is unreasonable in the case where the transmission period varies, particularly when the period of the beacon frames becomes shorter. That is, in the case where the transmission period of the beacon frame becomes shorter, the time errors between the coordinator and the device decreases. However, since the related art method turns on the transceiver based on the fixed time error and the transmission period without considering the decreased time errors, it is very inefficient.